How to use the command 'next' (with examples)

Next.js is a popular React framework known for its server-side rendering capabilities and the ease with which it allows developers to build optimized web applications. This command-line tool is used for various tasks, such as developing, building, and deploying Next.js applications. Below, we explore several use cases of the ’next’ command, providing insights into each scenario.

Use case 1: Start the current application in development mode

Code:

next dev

Motivation:

Running your application in development mode is essential for the ongoing process of building and testing new features, ensuring that changes can be seen immediately without having to manually rebuild your application every time. This mode provides hot-reloading, error reporting, and other helpful development features.

Explanation:

The command next dev tells Next.js to start the current application in development mode. This mode is specifically tailored for developers by enabling features that make it easier to track changes and debug the application in real-time. No additional arguments are necessary unless you want further customization like specifying a port.

Example Output:

After executing the command, you might see output indicating that the development server has started and is listening on a specific port (usually 3000). This output typically includes URLs to access your application locally.

ready - started server on 0.0.0.0:3000, url: http://localhost:3000

Use case 2: Start the current application and listen on a specific port

Code:

next dev --port 4000

Motivation:

You might need to run your development server on a different port to avoid port conflicts or to run multiple applications simultaneously. It’s crucial in environments where the default port is already in use or blocked by other applications or restrictions.

Explanation:

Here, next dev is used in conjunction with the --port argument. The --port argument specifies the port number that the server should listen on, allowing customization beyond the default port (3000). Adjust the port number as necessary to fit your development environment needs.

Example Output:

You will see a message confirming that the development server has started on the specified port:

ready - started server on 0.0.0.0:4000, url: http://localhost:4000

Use case 3: Build the current application optimized for production

Code:

next build

Motivation:

Before deploying an application, it must be built for production. This process optimizes the application by minimizing JavaScript and stylesheets, removing development-only libraries, and ensuring everything performs efficiently across browsers.

Explanation:

The command next build compiles the application and prepares it for production deployment. It performs various optimization tasks such as code splitting, tree shaking, and minification, which aren’t enabled during development.

Example Output:

Upon execution, the terminal should show a series of messages indicating the build process, concluding with a message that indicates the build was successful:

Creating an optimized production build...
Compiled successfully.

Use case 4: Start the compiled application in production mode

Code:

next start

Motivation:

Once your application is built, you want to test it in a production-like environment. Running the application in production mode is key for this, as it mimics how the application will run in your deployment environment.

Explanation:

The next start command initiates the application using the production build outputs created by next build. It leverages the optimized assets to serve the application efficiently to ensure a similar environment to live deployment.

Example Output:

The output will show the server start messages, typically indicating the application is running at default port 3000, ready for production-level testing:

started server on http://localhost:3000

Use case 5: Start the compiled application and listen on a specific port

Code:

next start --port 8080

Motivation:

As with development mode, it’s sometimes necessary to run your production server on a different port, which might be dictated by hosting providers or specific organizational infrastructure requirements.

Explanation:

Adding the --port argument to next start specifies a custom port for the production server. This allows flexibility in configuring the server environment or when dealing with port conflicts.

Example Output:

The server is started successfully on the designated port:

started server on http://localhost:8080

Use case 6: Export the current application to static HTML pages

Code:

next export

Motivation:

Some projects require static site generation where client capabilities are limited or to enhance performance and SEO advantages of a static site. Exporting as static HTML can be beneficial in such cases.

Explanation:

The command next export converts your Next.js application into a set of static HTML files. It crawls all routes of the app and generates static HTML for each, excluding any dynamic server-side content, which increases page delivery speed and reliability.

Example Output:

Post-execution, the console confirms the export with details about the HTML files generated for each route:

Export successful.

Use case 7: Display the Next.js telemetry status

Code:

next telemetry

Motivation:

Understanding your application’s telemetry status can provide insights into usage data collection, helping in improving the Next.js tooling and features with user feedback data.

Explanation:

Executing next telemetry displays whether telemetry reporting is currently enabled or disabled in your Next.js application. This feature involves sharing usage information with the Next.js team to aid in product improvements.

Example Output:

The command will output the current telemetry status:

Status: enabled

Use case 8: Display help for a subcommand

Code:

next build --help

Motivation:

Accessing detailed help for a specific subcommand can clarify usage and available options, ensuring correct and efficient use of the commands.

Explanation:

Using --help with any Next.js subcommand like next build provides a list of options, examples, and usage instructions, guiding users in exploring further command functionalities and options.

Example Output:

You will receive a comprehensive list of available options and usage instructions:

Usage: next build [options]
Options:
  ...

Conclusion:

The ’next’ command offers versatile options for developing, building, deploying, and understanding Next.js applications. Whether you are starting development, preparing for production, or seeking additional command descriptions, these examples demonstrate how different arguments and commands are used to optimize your workflow with Next.js.